NTSC and PAL are very fun. Using quadrature amplitude modulation to add color to the monochrome signal in a backward compatible way was so ingenious. PAL added things to make it better after some learnt lessons with NTSC, foremost the 180° phase shift with each lines, which cancels out phase errors.

(Fun facts: Because of that, countries with PAL instead of NTSC never knew what a "tint control" on the TV was, and the nostalgic 80s VHS look is also missing that blueish/purple color shift there.)

I wrote both an NTSC+PAL decoder in Matlab, and a PAL encoder in an FPGA (also fixed point), which I use in an actual project as composite video output. Decoders are harder and less straightforward than encoders, with lots of optimizing potential, because you need to filter the color signal out (I look forward to seeing what this code did). If you really, truly understand how NTSC and PAL work in their mathematical details, you may get your mind blown away by reading about this decoder, which is likely the best PAL decoder that ever existed: http://www.jim-easterbrook.me.uk/pal/

Writing my own encoder and decoder was super enlightening, and there are tons of details to nerd out on, e.g. when you get into data that's encoded into the sync gap for Videotext, closed captions, and other stuff.

In my dabblings with SDR, playing around with analog video was one of the highlights. Something about this technology that was such a prominent yet opaque feature of my youth and now being able to control it from the inside out felt extremely empowering.

I wrote my own decoder in python (nowhere near realtime) because at the time I couldn't find one that handled color. The deep dive on the design tradeoffs and signal processing hacks for NTSC was fascinating.

A few of my exploits below:

Full-frame decode of VHS w/ closed captioning: https://mrgris.com/a/ntsc-cc.mp4

Faithful reproduction of analog artifacts: https://mrgris.com/a/colorbars_slow.gif

Analog scrambling: https://www.youtube.com/watch?v=qceZgxSBHwo

Inject custom captions (it supports color!): https://mrgris.com/a/thanks.mp4

Sad that these signals are gone now... would have loved to play around with SAP/MTS, teletext, C-band...